Differential pressure controlled switch



Jan. 9, 1951 J. G. MEJEAN 2,537,474

DIFFERENTIAL PRESSURE CONTROLLED SWITCH Filed March 24, 1949 2 Sheets-Sheet l Jan. 9, 1951 J. G. MEJEAN 2,537,474

DIFFERENTJ'ZAL PRESSURE CONTROLLED swrrcn Filed March 24, 1949 2 Sheets-Sheet 2 IN VEN TOR. mamas d Mam/v I?" A rm/e/va Patented Jan. 9, 1951 DIFFERENTIAL PRESSURE CONTROLLED 'SWIT-CH v Jacques G. Mejean, Greenwich, :Gonm; :assignor to The .Aerotec Corporation, Greenwich, 1G0nn., a, corporation of (lonnecticut 'ApplicationiMarchiM, 1949;Serial*No.433,181 1 4 :Claims. (Cl..-20.08 3) vMy present invention relates to apparatus.con" trolled by pressurediiierences for the regulation or control :of mechanism.

.In -.my invention gases .or :fluids of different pressure areso balanced .as :to maintain acontrol element, such as -.an electric switch, in a neutral position for differences .of pressure .and to move it to actuating position inonedirection or another \upon changes in .the relative :pressures.

.For this .purpose my invention provides a pair of diaphragms of different reflective areas, the smaller of which is .expsedor subjected to the medium of higher pressure, and the larger .of which is subjected to the medium .oflower ,pressure, the idiaphragms -.being separated but connected to mOVe as a unit.

One of the diaphragmsis connected to an actuating or control mechanism, as a switch, swinging or pivoted between electriccontacts and preferably within the lower pressure medium so that with the :movement of the diaphragms the switch or element is moved in .one directionor the other. V T

.LMeans are provided for adjusting the -base-or support of the movable switch element :so that a very ifine .adjustmen't may belattaine'd. This is preferably done by means of a diiierential screw extendng through the wall of the enclosing case into the chamber containing thelow pressure fluid.

The various features of my invention are i1- lustrated, by way of example, in the accompany ing drawings in which Fig. 1 is a plan, -and Fig. 2 a side elevation of an apparatus embodying a preferred form of the invention;

Fig. 3 is a section of the apparatus taken on line 3-3 of Fig. 1; a

Fig. 4 is a section on a smaller scale taken on line 4--4 of Fig. 3, and

Fig. 5 is a diagrammatic illustration of the wiring of a circuit embodying the invention.

In the embodiment of the invention illustrated in the accompanying drawings, a pair of diaphragms l and II are mounted in spaced position within an enclosing case [2 in such manner as to separate the case into a high pressure chamber I3 an intermediate chamber l4 and a low pressure chamber 15. The diaphragm ll may be provided with rigid centrally disposed plates l6 and the diaphragm Hl may be similarly provided with rigid centrally disposed plates 11.

The plates 16 and I! are connected by means of :a spanning element or rod .18 which holds the diaphragmsin fixed spaced relation at their centers.

The case t2 may :be :made in three .parts, i9, 20 and 2|, between which the diaphragms ill and M :are clamped and held by means of bolts 22 which clamp the-elements of the case tightly together with spaces between the elements and diaphragms being sealed tight against air, gas or other fluids.

' interposed between the diaphragm l! and the case elements is :and 2c are rigid rings 23 and 24 on opposite sides of vthe diaphragm which limit or reduce the reflective [area ofthe diaphragm to the-areawithin these rings. The effective :torce acting on the diaphragm will, therefore, be the product of the pressure .of the gas and the area-of the diaphragm.

.Spacing rings 25 and Q26 maysi-milarly be provided .on .the opposite sides of the peripheral part of the diaphragm Hi, the inner peripheral diameter ofthe rings 25 and 26 being greater than that of .the rings .23 and 34 so that the effectivearea ofthediaphragm H3 will be greater than .that-of the diaphragm H and the pressure of the .gas required to balance the gas pressure in .the chamber [3 will consequently be much less.

The chambers I3 and I5 are provided with openings 2'! and 28 through which connection may be made to the different sources of pressure.

The intermediate chamber 14 is also provided. with an outlet 29 which may be open to the atmosphere or be connected to a source of uniform pressure, preferably intermediate that of the pressures in the chambers I3 and I5.

It will be evident that the diaphragms l0 and H and the connecting element [8 will be in mid position and balanced when there is a certain pressure differential between the chambers 13 and I5, and that when this difierential changes the diaphragms will be moved as a unit in one direction or the other.

The movement of the diaphragms is transmitted through a connecting stem or link 30 to a movable control element, such as a switch arm 3| pivotedon a stationary support 32 and movable between a pair of fixedelectrical contact terminals 33 and 34.

The terminals 33 and 34 are connected by means of conductors 35 and 36 to suitable actuating or control mechanisms.

The supporting base for the switch arm 3| may comprise a block of suitable material, such as an insulating compound, to which the switch arm 3|, which may be a leaf spring, is secured by suitable screws or rivets 31.

The supporting block 32 is mounted on the wall of the case by means of a stem 38 threaded as at 39 into an opening in the block 32 and extending through and rotatable in a projection 40 on the wall of the case.

The stem 38 is provided with an annular groove to form a resilient sealing ring 4|. And beyond this sealing ring is a second threaded length 42 threaded in and extending to the exterior of the projection 40. The threads 42 and 39 are inclined in the same direction but of different pitch so as to give a reduced movement to the block 32.

The block 32 is kept from rotation about the stem 38 by means of a pin 44 fixed on the case I 2 and engaging a slot 45 as shown in Fig. 4. The switch arm 31 is connected by means of a conductor 46 in a suitable electric circuit. The conductors 35, 36 and 4'6 pass out of the low pressure compartment through a fitting 41 in which they are sealed fluid-tight even at relatively high temperatures.

' The manner of operating the control apparatus is illustrated by way of example in Fig. 5 in which the reference numerals correspond to those in Fig. 3.

It will be apparent that as the movable switch element 3| contacts with the terminal 33 or 34 it will close a circuit to the wires 35 and 36 passing to an actuating element not shown.'

To prevent excessive movement of the diaphragm a pair of spaced stop rings 48 and 49 are provided on opposite sides of the diaphragm l0.

Through the above invention, therefore, a control element may be actuated by mediums of different pressure to remain in mid or neutral position for a predetermined pressure diiference, but to swing to one control element or the other as this pressure differential changes.

In use it is sometimes advantageous to connect the intermediate chamber Hi to a zone where pressures are near the value of the pressures transmitted to the chambers I3 and so as to have a small differential pressure across the dia- 4 phragm even though high absolute pressure conditions exist.

Having described my invention, what I claim is:

1. Differential pressure controlled apparatus which comprises a case, a diaphragm separating a part of said case into a chamber for higher pressure, a diaphragm of larger area separating a part of said case into a' chamber for lower pressures and spaced from the first mentioned diaphragm to form an intermediate chamber, said chamber for higher pressures and said chamber for lower pressures each having an outlet, a pair of spaced electric contact terminals in one of said pressure chambers, a swinging contact in said chamber to swing from one of said spaced contacts to the other, a connector connecting said diaphragm in fixed spaced position, a connector connecting said diaphragms to actuate said swinging switch, a support for said swinging contact and means operable through the wall of said case to adjust the position of said support relative to said spaced contacts.

2. The apparatus of claim 1 in which said adjusting means comprises a screw connection extending through and threaded in the wall of said case and threaded into the support of said swinging contact with a pitch different from that in the wall of said case. r

3. The apparatus of claim 1 in which said case is formed of an intermediate annular element and a pair of end elements and in which said diaphragms are secured between said elements.

4. The apparatus of claim 1 in which spaced stop rings are provided on opposite sides of one of said diaphragms. 1 I I JACQUES G. MEJEAN.

REFERENCES CITED The following references are of record in the file of this patent:, 9

UNITED STATES PATENTS 

